Setup for the Centerless Grinder 243
Setup for the Centerless Grinder explains how to set up a centerless grinder for typical outer diameter (OD) operations. The class explains the necessary setup for the work rest blade and regulating wheel angle of inclination, as well as the methods for selecting and mounting a grinding wheel. The class also explains the proper truing and dressing procedure for both the grinding and regulating wheel.
Centerless grinding results in close tolerances but only if the machine is properly set up for the operation. After taking this class, users will be able to describe the steps required to set up a centerless grinder for routine OD grinding of a cylindrical part.
Number of Lessons 16
- Setting up a Centerless Grinder
- Work Rest Blade Selection: Material
- Work Rest Blade Selection: Dimensions
- Regulating Wheel Angle of Inclination
- Regulating Wheel and Workpiece Feed Rate
- Work Rest Blade and Regulating Wheel Review
- Selecting a Grinding Wheel
- Detecting Grinding Wheel Imbalance
- Balancing Methods
- Grinding Wheel Review
- Mounting the Grinding Wheel
- The Sequence of Grinding Wheel Mounting
- Dressing and Truing
- Setting the Regulating Wheel Truing Angle
- Offsetting the Dresser
- Dressing and Truing Review
- Describe centerless grinder setup.
- Describe work rest blade selection.
- Describe work rest blade selection.
- Describe the regulating wheel angle of inclination.
- Describe the relationship between regulating wheel speed, angle of inclination, and workpiece feed rate.
- Describe factors that assist in selecting an appropriate grinding wheel.
- Identify grinding wheel imbalance.
- Describe various balancing methods.
- Explain how to mount the grinding wheel.
- Describe the process of dressing and truing a grinding wheel.
- Describe the truing angle for the regulating wheel.
- Describe offsetting the dresser for truing a regulating wheel.
A hard, sharp particle of material used to abrade away material. Common abrasive grains include aluminum oxide and silicon carbide.
A steel that contains elements other than carbon that give the steel superior properties, such as corrosion resistance and wear resistance, for certain applications. Common alloy steel alloying elements include chromium, manganese, molybdenum, nickel, and vanadium.
A two-dimensional space between two intersecting straight lines or flat surfaces, usually measured close to the point of intersection. Angles are measured in degrees or radians.
angle of inclination
The angle formed by the centerline of the regulating wheel spindle and the centerline of the grinding wheel. The angle of inclination allows the regulating wheel to provide the axial thrust that feeds the workpiece past the grinding wheel during centerless grinding.
arc of cut
The length of the arc formed at the point where the circular shape of the grinding wheel intersects with the circular shape of the workpiece when grinding occurs. A smaller arc of cut with the same stock removal rate increases the force on each individual grain in the grinding wheel and causes the wheel to wear away rapidly.
A precision device that detects vibration and corrects imbalance using one of several methods, including gases and fluids. Automatic balancers are used to balance grinding wheels when exact precision is required.
Running straight along or parallel to the axis of a workpiece. Axial as well as rotational movement are required for a workpiece to be properly ground during centerless grinding.
A force that pushes a workpiece straight along or parallel to its axis during centerless grinding. Axial thrust is provided by the regulating wheel.
A wheel that has equal weight and shape throughout making it run completely concentric with the axis of the machine spindle. A balanced wheel does not vibrate unless acted upon by external forces.
A tool with two points equal in height on which a wheel on a mandrel can be set. Balancing stands can be used to detect wheel imbalance.
Needle-shaped diamonds layered into a pattern to form a blade. Blade dressers are used to dress a grinding wheel when the operation requires precision.
A paper ring that helps ease mounting pressures between the wheel and the flange. Blotters are often placed between flanges and the grinding wheel to help prevent damage caused by tightening.
The material that holds abrasive grains together in a grinding wheel. Bond, or bonding material, can be vitrified, resin, rubber, or metal.
A type of steel that is formed into its final shape from the molten state. Cast iron contains at least 2.11% carbon.
A type of cylindrical grinder in which a cylindrical part is supported on a work rest blade and guided between a grinding wheel and a regulating wheel. Centerless grinders drive the workpiece using the regulating wheel, and the grinding wheel grinds the workpiece surface.
A type of cylindrical grinding process in which a cylindrical part is supported on a work rest blade and moved axially between a grinding wheel and a regulating wheel. Centerless grinding drives the workpiece using the regulating wheel, and the grinding wheel grinds the workpiece surface.
An imaginary line that defines the theoretical center of a workpiece or workpiece feature and halves or runs axially through the center of a cylindrical object. The centerline of a cylindrical workpiece is its theoretical axis of rotation.
ceramic aluminum oxide
A ceramic compound in the form of either a white powder or colorless crystals. Ceramic aluminum oxide is commonly used as an abrasive material.
A material consisting of compounds formed by metallic and nonmetallic elements. Ceramics include traditional materials such as brick and clay, as well as advanced ceramics used as abrasives, cutting tools, or electronic components.
Surface imperfections on the workpiece caused by vibrations of the grinding wheel. Chatter marks occur when an out-of-balance wheel vibrates at a high speed.
A small piece of material that is removed from a workpiece. Chips are formed when a tool cuts or grinds a material.
cluster-type diamond dresser
Several diamond stones mounted evenly across a steel nib. Cluster-type diamond dressers are used to dress grinding wheels on large grinders for operations that require less precision.
Hollowed out or curving inward. Concave regulating wheel surfaces result from the tilted regulating wheel being dressed parallel to the path of the workpiece, which is the truing angle and often the same as the angle of inclination of the regulating wheel.
Having a common center or sharing the same axis. The concentric circles that make up a grinding wheel periphery should share a center point on this axis.
A three-dimensional form tolerance that describes the allowable variability in the shape and appearance of a cylinder. Cylindricity states how close a part is to being perfectly cylindrical.
An object's deviation from a straight line or plane when a force is applied to it. Deflection should be minimized during a centerless grinding operation by using a work rest blade made of a hard material.
A unit of measurement used to indicate the size of an angle. A complete circle contains 360 degrees.
The distance from one edge of a circle to the opposite edge, as measured through the center. The diameter of a workpiece will be consistent with accurate setup of a centerless grinder.
A naturally occuring or manufactured stone made of crystalline carbon that is used as an abrasive because of its extreme hardness. Diamond is the hardest available material.
diamond wafer roll
A cylindrical dressing tool with diamonds embedded in its periphery. Diamond wafer rolls are sometimes used to dress a wheel when the grinding operation requires precision.
double angle V-blades
A work rest blade that supports a workpiece between two surfaces that form a V shape. Double angle V-blades are not as dependent on work guides as a single angle blade but their surface wears more rapidly.
To remove swarf, dull grains, and bonding material from an abrasive wheel by fracturing away the wheel surface. Dressing conditions the surface of the grinding wheel such that it produces the required surface finish with the most economical stock removal rate.
A tool made of diamond or metal that is used to remove material from the surface of a grinding wheel. Dressers are used to dress and true a grinding wheel.
Removing swarf, dull grains, and bonding material from an abrasive wheel by fracturing away the wheel surface. Dressing conditions the wheel surface so that it is prepared for stock removal or high surface finish.
electrical feeding mechanism
A device powered by electricity that controls the rate at which the dressing tool travels across the grinding wheel. Electrical feeding mechanisms are set to run at a rate of traverse that depends on both the shape and size of the dressing tool in order to achieve the desired workpiece finish.
A method of centerless grinding in which the workpiece is fed into the grinding and regulating wheels until the workpiece contacts an end stop. Endfeed centerless grinding may be used to taper the end of a workpiece or grind features that increase in diametric size in the direction of axial travel.
A flat or raised metal disk that is often used to mount grinding wheels on their spindles. One flange is used on each side of the grinding wheel to clamp the wheel on its sides.
The ability of an abrasive grain to fracture and self-sharpen under stresses of the grinding process. Friability requirements for centerless grinding wheels depend on many factors, one of which is the workpiece diameter in combination with the radial stock removal rate that affects the arc of cut length.
A letter designation that describes the hardness of a material. The grade of a grinding wheel will be any letter from A to Z, where A is the softest and Z is the hardest.
A wheel made of abrasive grains that are held together by a bonding material. A grinding wheel rotates and grinds away microscopic chips of material and can produce very fine surface finishes.
The ability of a material to resist scratching, abrasion, indentation, or cutting. Hard materials generate more heat and are more difficult to machine.
Held in place by a workholding device. Hard-fixtured workpieces are less prone to experiencing vibration than workpieces involved in centerless grinding.
HSS. A category of tool steels used for cutting-tool applications. High-speed steel stays hard at high temperatures and resists abrasion.
A material's ability to resist the forces that attempt to pull it apart or stretch it. The tensile strength of a workpiece is one of the factors that determine both the type of abrasive grain and the bond strength of a centerless grinding wheel.
hydraulic feeding mechanism
A device powered by fluids that controls the rate at which the dressing tool travels across the grinding wheel. Hydraulic feeding mechanisms, though not as accurate as electrical systems, are set to run at a rate of traverse that depends on both the shape and size of the dressing tool in order to achieve the desired workpiece finish.
An uneven distribution of weight around a rotating object. Imbalance causes a grinding wheel to vibrate at high speeds.
Referring to Inspection that occurs while a part is being machined. In process inspection must be performed by centerless grinding operators to check grinding and regulating wheels.
inches per minute
ipm. A unit of measurement for feed that indicates how many inches the grinding wheel, dressing tool, or workpiece has traveled in one minute. Inches per minute is an English measurement.
A form of centerless grinding that involves the regulating wheel and work rest blade holding the workpiece against a stop as the grinding wheel feeds axially into the part. Infeed centerless grinding has an angle of inclination that rarely exceeds 0.25 degrees.
inches per minute. A unit of measurement for feed that indicates how many inches the grinding wheel, dressing tool, or workpiece has traveled in one minute. Ipm is an English measurement.
A measurement of linear distance from one point to another. Length is measured in inches or feet in the English system and centimeters or meters in the metric system.
A type of nut that screws down on top of another nut to hold the first one in place. A lock nut holds the different parts of a sleeve together.
low carbon steel
A metal consisting of iron and a low amount of carbon, usually with small amounts of other elements. Steel is the most common manufacturing metal.
meters per second. A measurement of speed that is a direct function of the workpiece or grinding wheel diameter and its rate of rotation. M/s is a metric measurement.
The spindle or post on which a wheel is mounted. A mandrel can then be placed on a balancing stand to test for wheel imbalance.
The substance out of which something is made. Materials commonly used to make work rest blades include high-speed steel, cast iron, tungsten carbide, and, sometimes, steel coated with Stellite.
Characteristics of metal that describe its qualities and capabilities. Metallurgical properties include a variety of physical and mechanical properties such as strength.
meters per minute
m/min. A unit of measurement for feed that indicates how many meters the grinding wheel, dressing tool, or workpiece has traveled in one minute. Meters per minute is a metric measurement.
meters per second
m/s. A measurement of speed that is a direct function of the workpiece or grinding wheel diameter and its rate of rotation. Meters per second is a metric measurement.
A numerical value used to reposition machine components. Offsets are used to adjust for differences in wheel geometry, part size, and wheel wear.
A grinding wheel that rotates on a spindle so that the wheel's centerline of gravity does not lie directly parallel and in line with the spindle's centerline of rotation. An out-of-balance wheel usually has one heavier side.
A centerless grinding problem that occurs when excessive pressure and heat from the process cause tiny chips to fuse to the blade. Pick-up, also called scoring, often occurs when there is insufficient lubrication between the workpiece and the blade.
rate of traverse
The speed at which the dressing tool travels across the grinding wheel. The rate of traverse for a dressing tool is critical in order to achieve the desired condition on the surface of the grinding wheel and is best controlled by an electrical feeding mechanism.
A wheel commonly made with a resin bond that is used to control the speed of the workpiece both axially and rotationally as it is fed along the work rest blade and past a grinding wheel. A regulating wheel, or control wheel, also drives the workpiece axially across the work rest blade.
regulating wheel housing
The part of a centerless grinder on which the regulating wheel is mounted. The regulating wheel housing is tilted to adjust the angle of inclination.
revolutions per minute
rpm. The number of revolutions that a spindle completes in one minute. Revolutions per minute is a rate of rotation.
The rate of rotational movement of the grinding or regulating wheel. Spindle speed is measured in revolutions per minute (rpm).
The quality of a cylindrical workpiece characterized by its entire length having the same diameter relative to a common axis. Perfect roundness means that all points on the exterior surface of a cylindrical workpiece are equidistant from the workpiece centerline.
A centerless grinding problem that occurs when excessive pressure and heat from the process cause tiny chips to fuse to the blade. Scoring, also called pick-up, often occurs when there is insufficient lubrication between the workpiece and the blade.
The series of tasks necessary to prepare for processing a workpiece. Setup includes preparing machines, adjusting workholding devices or tooling, and safeguarding machine elements to ensure proper and safe operation.
SIN. The ratio of the length of the opposite side to the length of the hypotenuse of a right triangle. The sine of a regulating wheel angle of inclination is used to calculate the workpiece feed rate.
single angle blades
A work rest blade that supports a workpiece on one angled surface. Single angle blades are usually angled to 30 or 45 degrees.
single-point diamond dresser
A diamond stone mounted in a steel nib. Single-point diamond dressers are used to dress grinding wheels for precision grinding operations.
A type of flange that consists of two differently shaped parts that fit together and are secured by a lock nut. A sleeve can be used to mount a grinding wheel onto a grinder.
The ability of a grinding wheel to remain at rest in any position when placed on a balancing stand. Static balance means that a grinding wheel has no heavy side.
A wear-resistant alloy made of cobalt and chromium. Stellite is sometimes used to coat the working surface of a steel work rest blade.
stock removal rate
The amount of material removed from a workpiece in one pass of the grinding wheel. The stock removal rate influences a wheel's friability.
The ability of a metal to resist forces that attempt to break or deform the metal. Strength helps minimize vibration and deflection of work rest blades, but it can also cause scoring.
surface feet per minute
sfm. A measurement of speed that is a direct function of the workpiece or grinding wheel diameter and its rate of rotation. Surface feet per minute measures the number of feet that a location on a rotating component travels in one minute.
The smoothness of a part surface after it has gone through all grinding operations. Finish is the complete, desired surface.
A measurement of how wide something is. The thickness of a work rest blade is always smaller than the workpiece diameter.
A method of centerless grinding in which the workpiece rests on the work rest blade and the regulating wheel rotates and feeds the workpiece past the grinding wheel in a straight line. In throughfeed grinding, the regulating wheel moves the part completely past the grinding wheel.
The rate at which the workpiece passes axially between the grinding and regulating wheels. Throughfeed rate is controlled by the regulating wheel.
The acceptable deviation from a given dimension. Tolerances indicate the allowable difference between a physical feature and its intended design.
The ability of a material to withstand forces or sudden impacts that attempt to break it. Tough materials can withstand sudden stress.
To restore a grinding wheel to its original, intended shape. Truing ensures that a wheel retains a circular shape concentric with its axis.”
The angle necessary for the truing device to create a slightly concave regulating wheel face.The truing angle matches the regulating wheel angle of inclination for small workpieces.
A compound of tungsten and carbon that is commonly used to make metal-cutting tools. Tungsten carbide has excellent hardness and is commonly used to make work rest blades.
The continued, repetitive, periodic, back=and=forth motion in a machine or other structure. Vibration should be minimized during a centerless grinding operation.
Referring to a material's ability to resist the gradual wearing away caused by abrasion and friction. A wear-resistant material is sometimes used to coat a steel work rest blade.
The breakage of a grinding wheel. Wheel failure poses a safety hazard to operators.
A centerless grinder component located at the beginning and end of the machine to position the workpiece as it enters and exits. Work guides, or work rest guides, are used for throughfeed centerless grinding.
work rest blade
A device that supports cylindrical parts during centerless grinding. Work rest blades often have an edge that angles toward the regulating wheel.
A part that is in the process of being manufactured. A workpiece may be a complete product by itself or one component of a product consisting of many parts.
Restoring a grinding wheel to its original, intended shape. Truing ensures that a wheel retains a circular shape concentric with its axis.
To retain a grinding wheel's circular shape concentric to its axis using a dressing tool. Truing ensures that a wheel's axis of rotation is the same as that of the machine spindle.